Couldn't find the t550.uk on the Crucial website but I did find it on the Kingston site
here.
Obviously to get the full 2GB you'll need 2 x 1GB modules and replace whatever is in the machine already (I would assume it would be a single 512MB module). And of course you don't need to buy Kingston, but this should help you identify what type of module to look for that would be compatible.
HTH.